GNU bug report logs - #6936
Bug#594666: /usr/bin/tac: tac aborts

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Message #16 received at 6936-done <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: 6936-done <at> debbugs.gnu.org
Subject: Re: Bug#594666: /usr/bin/tac: tac aborts
Date: Sun, 07 Aug 2011 18:22:38 +0200

Jim Meyering wrote:
> Salvo Tomaselli wrote:
>> Package: coreutils
>> Version: 8.5-1
>> Severity: normal
>> File: /usr/bin/tac
>>
>> Tac aborts when using it on a particular file.
>>
>> *** glibc detected *** tac: double free or corruption (top):
>> 0x00000000025c5030 ***
> ...
>
> Thank you for the report!
> That is indeed a bug in the very latest.
>
> For a stand-alone, minimal demonstrator, run this:
>
>     valgrind tac <(printf %0$((2**14 + 1))d 0) > /dev/null
>
> It prints this:
>
>      Invalid free() / delete / delete[]
>         at 0x4A04D72: free (vg_replace_malloc.c:325)
>         by 0x402294: main (tac.c:669)
>       Address 0x4c30040 is 0 bytes inside a block of size 16,388 free'd
>         at 0x4A05255: realloc (vg_replace_malloc.c:476)
>         by 0x4117B8: xrealloc (xmalloc.c:57)
>         by 0x401A68: tac_seekable (tac.c:319)
>         by 0x402379: main (tac.c:515)
>
> Here is a fix:
>
>>From b3959fc691e606857a3c6e9b316ec34819972245 Mon Sep 17 00:00:00 2001
> From: Jim Meyering <meyering <at> redhat.com>
> Date: Sat, 28 Aug 2010 17:45:29 +0200
> Subject: [PATCH] tac: avoid double free
>
> * src/tac.c (main): Reading a line longer than 16KiB would cause
> tac to realloc its primary buffer.  Then, just before exit, tac
> would mistakenly free the original (now free'd) buffer.
> This bug was introduced by commit be6c13e7, "maint: always free a
> buffer, to avoid even semblance of a leak".
> * NEWS (Bug fixes): Mention it.
> * tests/misc/tac (double-free): New test, to exercise this.
> Reported by Salvo Tomaselli in <http://bugs.debian.org/594666>.

This was fixed long ago.
Marking as "done".

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